The present invention relates to a laminated hose for fuel transportation (hereinafter sometimes referred to simply as a fuel hose) made of a fluororesin laminate excellent in heat resistance, antistatic properties and fuel impermeability. More specifically, it relates to a fuel hose wherein an inner layer and an outer layer are both made of a fluororesin.
Further, the present invention relates to a fuel hose which has a corrugated region midway and thus is capable of warping, shrinking or twisting, whereby it can be mounted in an engine room of an automobile without being subjected to bend processing.
Fluororesins such as ethylene/tetrafluoroethylene copolymers (hereinafter referred to also as ETFE), tetrafluoroethylene/hexafluoropropylene copolymers (hereinafter referred to also as FEP) or vinylidene fluoride polymers (hereinafter referred to also as PVdF), are excellent in chemical resistance, weather resistance and surface properties and thus are used in a wide range of fields. For example, films of such fluororesins are used as surface coating materials for substrates made of an inorganic material such as metal or glass or made of an organic material such as a synthetic resin. Further, a laminate of a fluororesin sheet and a sheet of other base material, is used for e.g. a hose for fuel transportation for automobiles, or a hose for transportation of an industrial reagent, which requires chemical resistance, and the fluororesin layer is employed usually as a barrier layer to prevent permeation of the fuel component to be transported, as the inner layer.
Usually, the fuel hose has a multilayer structure wherein the barrier layer to prevent permeation of the fuel component to be transported, as the inner layer, is a fluororesin, and an outer layer of polyamide 6, polyamide 11, polyamide 12, etc., is laminated thereon via an adhesive layer. However, as recycling is desired as an attempt to preserve the global environment, a component having such a multilayered structure has a problem that recycling tends to be very difficult.
In addition, the fluororesin has high insulating properties, and when such a fluororesin is used as an inner layer, charges are likely to be built up especially during the passage of liquid and gas fuels, whereby there will be a possible danger of inflammation or explosion by electric discharge. Accordingly, antistatic treatment of the fluororesin is required.
Further, with a view to preservation of the global environment, it has been required in recent years to clean a combustion exhaust gas such as CO2, NOx, SOx, etc., discharged from a mobile source such as an automobile, or to suppress the discharge of such exhaust gas. At the same time, a strict total amount control of exhaust gas is enforced including prevention of leakage into atmospheric air by diffusion of e.g. volatile fuel hydrocarbons through a fuel transportation hose wall of a fuel piping system and a gas discharge system. However, in order to cope with deterioration of the environment on a worldwide scale, even stricter regulations are being considered, and according to observations by the present inventors, it is imperative that in near future, the leakage amount of volatile hydrocarbons from a fuel hose wall will be required to be substantially lower than the measurable limit.
Heretofore, fuel hoses having various material constitutions have been proposed as fuel hoses having the fuel barrier properties improved to be used for fuel piping systems and gas exhaust systems for automobiles, but they can hardly be regarded to be sufficient to meet such strict regulations whereby it is required to reduce the amount of permeation/leakage of hydrocarbons substantially to the limit, as mentioned above.
Namely, the amount of leakage of hydrocarbons per vehicle will be regulated stricter from current at most 2 g/day to at most 0.2 g/day. In such a case, the amount of leakage of hydrocarbons per the outer surface of the hose will be required to be at most 0.01 g/m2xc2x7day, preferably at most 0.001 g/m2xc2x7day (substantially at most the detectable limit) in the line of the fuel transportation hose i.e. the unit portions provided with connectors for connection at both ends to lead the fuel from the fuel tank to an injector of an engine.
Further, conventional fuel hoses can not be said to have an adequate performance for prevention of leakage of fuel hydrocarbons at a region where the environmental atmospheric temperature is high, such as an engine.
Further, a fuel hose is subjected to bending at various angles over the entire length of a straight tube prepared by extrusion molding, in order to meet the positioning or special restrictions by a specific structure of each automobile. The bending of a hose not only brings about an increase of a process step but also brings about possible formation of creases. If creases are formed, a stress will be concentrated at the regions, whereby there will be a problem that the useful life of the hose tends to be substantially shortened.